Electric conveyor system



Oct. 14, 1941. E, U, LA SEN 2,258,775

ELECTRIC CONVEYER SYSTEM Filed Nov. 18, 1959 4 Sheets-Sheet l Oct. 14, 1941.

E. U. LASSEN ELECTRIC CONVEYER SYSTEM Filed Nov. 18, 1959 FLOOR 3 FLOOR ,8

4 Sheets-Sheet 3 num -"m...

Oct. 14, 1941.

E. U. LASSEN ELECTRIC CONVEYER SYS TEM Fi'led Nov. 18, 1939 4 Sheets-Sheet 4 l Z(I)5 20? 3.10

Patented Oct. 14, 1941 ELECTRIC CONVEYOR SYSTEM Eivind U. Lassen, Whitefish Bay, Wis., assignor to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Application November 18, 1939, Serial No. 305,101

Claims.

The present invention relates to electric conveyor systems and especially to elevator systems of the push button type in which one or more conveyors or elevators may be controlled from push button stations at the various landings and/or push buttons in the car in such a manner that the car stops in succession at the various landings for which push buttons have been operated in the natural order of such landings and so that the car completes its travel in a given direction before it reverses to respond to push buttons which have been operated to require the car to travel in the opposite direction.

An object of the invention is to provide an elevator control system requiring a minimum of apparatus to accomplish the aforediscussed results.

Another object is to provide a system which employs a control panel, the construction of which is independent of the number of elevators in an installation or the number of floors served.

Another object is to provide a system which can readily be adapted to any desired number of elevators to either operate independently or jointly to serve a plurality of floors.

The accompanying drawings are illustrative of several embodiments of the invention.

In the drawings,

Figure 1 is a circuit diagram of the control circuits of a system comprising two elevators which operate jointly.

Fig. 2 is a schematic diagram of the electromagnetic switches and relays employed to form the control panels for the motors which form a part of the control system of Fig. 1.

Fig. 3 is a general representation of the two elevator cars including their driving motors and their relation to several of the elements of the control system.

Fig. 4 is a schematic drawing of the push buttons employed in the system, while Figs, 5 and 6 are diagrams of a modification of the system of Fig. 1 and designed for a single elevator installation.

Referring to the drawings Figs. 1 to 4, the same illustrate two elevator cars l and 2, which are operated by reversible three phase alternating current motors 3 and 4, respectively. The motor 3 is supplied with energy through a main switch 5 and a pair of reversing switches 6 and T, the main switch 5 having a magnetizing winding 5 normally open main contacts 5 and 5, and normally open auxiliary contacts 5 5 and 5 The switch 6 is provided with a magnetizing winding 6 normally open main contacts 6' and 6, normally open auxiliary contacts 6 and normally closed auxiliary contacts B The switch 1 is provided with a magnetizing winding 1*, normally open main contacts 1 and 1 normally open auxiliary contacts I and normally closed auxiliary contacts 1 The car by means of a counter-weighted rope 8 running over a sheave 9 drives a number of selector switches so that their operation is a function of the position of the car. A rotating drum selector switch I0 is provided with two substantially semi-circular contact segments Ill and m respectively, and is arranged so that it makes substantially onehalf revolution for the full travel of the car in the hatchway. The segments l0 and 10 are provided with contact brushes 10 and I 0 respectively, which are continuously in engagement with the respective segments to conduct current thereto. A series of contact brushes 10 to I0 inclusive, corresponding to the number of floors is arranged about the circumference of the segments to make contact with one or the other depending upon the position of the car in the hatchway. There are further provided two travelling nut selector switches H and I2 which are geared to the drum 9 to move therewith. The switch H is provided with a segment II- and a series of floor contacts li H and li which are selectively connected to the segment H by a bridging contact II attached to the travelling nut. A second bridging contact II is adapted to bridge across a segment H and contacts ll II and il The selector switch I2 has a bridging contact l2 with a cooperating segment 12 and contacts I2 I 2 and I2 and a bridging contact l2 with a cooperating segment l2 and contacts I2 [2 and I2 Mounted on the various floors are push button stations l3 to 16, inclusive, as will be explained more fully hereinafter. There is also provided a retiring cam limit switch operating mechanism I! on the car comprising an operating magnet having an energizing coil I! which when deenergized actuates a cam I! so that when the car moves through the hatchway it abuts the lever I8 of a limit switch [8 mounted near the first floor in the hatchway to open a normally closed contact l8 of the latter. Similar limit switches l9 to 2|, inclusive, are mounted at the other floors. A push button station 22 is mounted inside of the car.

The floor push button stations [4 and I5 each comprise an up button switch l4, l5 and a down button switch M I5 respectively, while 2. Mil

the station I3 has only an up switch l3, and station IE only a down switch I6.

All of the push button switches are alike in construction and are shown more in detail in Fig. 4. The switch comprises a pair of stationary contacts I3 and I3 which are adapted to be bridged by a bridged contact I3 which is attached to the push button I3 The bridging contact I3 is normally held out of engagement with the stationary contacts by a biasing spring I3 and is provided with an abutment I3 which. is adapted to engage a latch I? to hold the bridging contact in the engaged 'p'ositionwhen the button has been depressed. To again release the latch and open the contacts the switch is provided with a tripping magnet I3 which when energized retracts the latch I3 against the bias of a spring I3 to thus open the push button contacts. One terminal of the magnet windingis connected to the bridging contact which thus deenergizes the magnet when the bridging contact is released.

The controller for elevator car I further comprisesithe following: Relay 23 has an energizing coil 23 normally open contacts 23 and normally'closed contacts 23. Relay 2% has an energizing coil 25 and normally open contacts 25 Relay 25 has an energizing coil 25*, and normally open contacts 25'. Relay 26 has an energizing coil 25%, and normally open contacts 25* Relay 21 has an energizing coil 21*, normally open contacts 2'5 21, 21 and 21 and normally closed contacts 27 Relay 23 has an energizing coil 28*,and normally open contacts 28". Relay 29 has an energizing coil 29 and normally closed contacts 29*. Relay 30 has an energizing coil 38, normally open contacts 39 36, 39 and 39 and normally closed contacts 39. Relay 3i has an energizing coil si and normally open contacts 31 The car push button station 22 is provided with floor push buttons 32 to 35, inclusive, which are in construction and operation similar to that illustrated in Fig. 4. In addition, the station 22 includes a momentary normally open contact starting push button 36, and a momentary normally open contact by-pass push button 31. The system mayalso include a number of the conventional safety devices, such as door switches, etc., which are connected in the usual manner to stop the car and which are generally designated in the drawing by the numeral 38..

The second elevator is provided with control instrumentalities identical to those just described for car I, as indicated in the drawing. Where required in the description of operation of the system, the elements of the second elevator have been designated by adding 100 to the numbers of the corresponding numerals of the elements for car I, hence the controller for car 2 needs no further explanation, as it is selfevident from the foregoing description and the drawing.

The operation of the system is as follows: With the apparatus connected as shown, and power on busses L L car I is at rest on the first floor, and car 2 is on the second floor. If now the operator of car 2 desires to start the car, he may start it in either the up or down direction. If he wishes to start it in the up direction he presses'fioor button I35, for instance, thereby establishing a circuit from L over contacts I35, brush H8 segment IIIl brush uec, normally closed contact I'3il coil I211 to L Relay I 2! opens contacts I21 and closes contacts I27 I21 I27 and 121". A circuit is thereby established from L over contacts I21 I01 coil Ififi to L This closes the up direction reversing switch main contacts I06 I I36, but the motor cannot start, as the motor main switch 565 is de-energized. If now the operator pushes the button I31, a circuit is established from L over contacts I3 6, through coil I to L Relay I24 closes contacts I2 3 and thus a circuit is established from L over contacts I'fi6 contacts I24 I23, coil Ii? to L Upon energization of coil li'l the retiring cam mechanism tends to complete a circuit, subject to prior closure of the various safety switches, such as door switches, indicated in the diagram as safety contacts I38, said circuit extending from L over contacts H36, I33, MS to IZi, inclusive, coil IE? to L The energizaticn of coil I closes the main switch 'contacts for the motor and the latter lifts the elevator.

If now the car reaches the fourth floor, the limit switch HI energizes the coil I35 of v.the push button I35 through a circuit from L over contacts 135, coil 535, contacts Hi lit HI, I27 coil I25 to L Coil i35 thereupon causes opening of said push button.

Completion of the circuit through coil I25 efiects closure of contacts iEE and thus simultaneously energizes momentarily relay coil IZS through contacts Ififi Relay I23 makes its own maintaining circuit through contacts I23 and opens contact 523 which de-energizes coil Ill of the retiring cam, thus opening limit switch contact i2 I (Figs. 1 and 3) andde-energizing coil Hi5 which opens the supply to the motor. and stops the elevator. It will be noted that when the car reaches the fourth i'ioor the circuit is also opened in selector switch IIii between brush H6 and segment lit, but energization of relay coil i2! is'continued through contacts Iii-5 E21 and I35 until the main switch I65 is de-energized, thus preventing interference of another call button with the operation of the car. It will further be noted that relay i2? remains energized as long as any buttons in the up direction maintain a contact for said relay through limit switch Hi3, and as long 'as relay I21 is'energized relay I59 cannot respond to permit travel of the car in the down direction. Thus by pressing either button I32 or 35 the operator may determine the direction of travel of the car which is 'then maintained until all landing buttons pressed for that direction have been'answered.

When the car has reached the highest floor for which any up push button had previously been depressed,'and a down push button was previously closed, for'instance, the button Ni the operator starts the car in the 'downdirection by closing button I32 thus energizing the coil I-Eil o'f relay I38, thereby establishing direction of travel, and then pushing the button I37, whereupon the coil m of relay I24 is energized, thus energizing motor switches I65 and 'Iil'I. in 'a manner similar to that aforediscussed, and the motor is started in'the down direction. As the elevator approaches the second landing a circuit is established from L over button I4 coil i i ,'limit switch II-2,,contacts I3I3 coil isl contacts I29 to L This energizes relay ISI, thus completing a circuit from Dover contacts I di I35 'IBBQ, coil I23 to L In responding, relay I23 opens contact I23 which de-energizes coil Hi of the retiring cam, whereupon the cam opens limit switch contacts 'II9, therebyIde-energizing the main switch I05 and bringing the motor to a stop. This permits opening .of the doors, which opens safety contacts I38, and the car cannot be restarted until all said safety contacts are closed again.

It will be noted that when once started in a given direction by the operator, the car will continue to proceed in that direction to stop on any floor for which buttons have been pressed, but it will not stop on such floors on which buttons for travel in the opposite direction have been depressed, such buttons remaining closed until finally the car moves in the desired direction, when it will stop at the respective floor.

Push button I36 when depressed by the operator energizes relay coil l29-'-', said relay when energized opening contacts 129*, so that the car in passing any floor for which a floor button has been depressed will not respond thereto, as the energization of the relays I28 and I3! is prevented. Thus the operator can by-pass any floor if he so desires.

The operation of car I is similar to that of car 2 which has just been described. The system further provides that whichever car first reaches a floor on which a call button has been depressed for the proper direction, will stop in response thereto. For instance, if car 2 on its up travel approaches floor 3, at which button l has been pressed, and reaches said floor before car I reaches it, travelling in the same direction, relay coil I28 is energized to initiate stopping of the car, while at the same time the push button l5 is released, thus making ineffective the setup for energization of relay 28 through limit switch 12, which would otherwise cause stoppage of car I. It is thus apparent that by the latched-in push buttons the selective stoppage of the first car reaching the floor from which a call originates is provided for in a simple and efficient manner.

It is obvious that the system may be extended for any number of cars and any number of floors, and it will also be apparent that the system may be used with a one-car installation by omitting selector switches l2 and H2 and relays 28, 3!, I28, l3l, and connecting the floor button stations 13 to I6, inclusive, to the proper elements of the remaining selector switches.

The system may, of course, be used in combination with the usual automatically operating doors and various signal devices. It may equally be adapted to various types of power supply and motors and their control.

The system illustrated in Figs. 5 and 6 is a modification of the previously described system and is shown as applied to the control of a single elevator. In this system, whenever a push button, either on a floor or in the car, is pressed to call the car to a difierent floor from the one on which it is at the time, the car upon closure of the doors will proceed to the next floors for which buttons have been pressed and stop successively at all such floors in the natural order of such fioors.

The system comprises a car (not shown) including floor limit switches, the latter being similar to switches I8 to 2! in Fig. 3, and designated together with door switches and other safety switches by the numeral 225, a retiring cam mechanism (not shown) which may be similar to the retiring cam l1, and other conventional accessories of an elevator as will be explained hereinafter. The car is operated by a reversing 3-phase motor 203 which is controlled by a double pole electromagnetic main switch 205 and a pair of double pole electromagnetic reversing switches 206 and 201. The m Switch 205 is provided with an energizing coil 205 normally open main contacts 205 and 205, and normally open temporarily closed auxiliary contacts 205 and 205 The bridging contact of contacts 205* is connected to a piston 205 of a dash pot 205 which in turn is mounted on a fixed support. The bridging contact is lifted into engagement with the stationary contacts by an abutment 205 on the operating rod of switch 205 so that the contacts 205 are closed when coil 205 is energized. Upon de-energization, the bridging contact is held in engagement to maintain its circuit temporarily closed until suflicient air has leaked out of the dash pot to permit descent of the piston by gravity and opening of the auxiliary contacts 205 The construction and operation of contacts 205 is the same as that just described, except that the time delay in opening of contacts 205 is slightly greater than that of contacts 205*. The reversing switch 206 is provided with an energizing winding 206 normally open main contacts 206 and 206, and normally open auxiliary contacts 206 205 206 and normally closed auxiliary contacts 206 Switch 201 is provided with an energizing winding 201 normally open main contacts 201 and 201, and normally open auxiliary contacts 201 201 and 201 and normally closed auxiliary contacts 201. There is further provided a relay 208, having an energizing winding 208 and normally open contacts 208 a relay 209 having an energizing winding 209 and normally open contacts 209, and a relay 2|0 having an energizing winding 210 and normally closed contacts HM, and normally open contacts 2l0c.

The system also includes double pole latchedin push button switches 2H, 2l2, 2l3 and 2, one for each floor, respectively, in the car. These push buttons are similar to those shown in Fig. 4, except that they are equipped with an additional set of normally open contacts, as shown in the diagram. Furthermore, each intermediate landing or floor is equipped with an up and a down push button switch, while each of the terminal landings is equipped with a single push button switch. These switches are designated in the diagram by the numerals 2l5 to 220, inclusive. A rotating drum selector switch 22! is similar to switch I0 of Fig. 1, and is connected to the car in the manner shown in Fig. 3. A travelling nut selector switch 222 is similar in construction and operation to the two halves of the selector switch H of Figs. 1 and 3. A retiring cam mechanism 224 which may be similar to mechanism 11 shown in Fig. 3 is represented in Fig. 5 by an energizing coil 224 the floor contacts which are operated thereby and the safety contacts together with the floor limit switches being designated by the numeral 225, as mentioned heretofore.

The system is connected and operates as follows: Let it be assumed that the car has come to a stop on the second floor and has discharged its passengers. If no push buttons are closed, the car will stay at the fioor with all switches 225 closed, except the floor switch of floor 2. If, however, the push button 2I3 is depressed, to call the car to the third floor, a circuit is established over limit switch 22!, contact 201 and coil 206 whereupon reversing switch 205 is energized to close its main contacts and also contacts 206 206 and 200 This completes a circuit over contact 206 contact 210 and coil 224 to L s 'that t m' is etired t e ct comp etion o a cir u p v ded t at all i the afe s tch 2 a los d- Thus a i cu is completed through switches 225 and coil 2 05 to energize the main switch 205, which clOSes its contacts to complete the motor circuit, and the motor causes the elevator to travel upward. Switch 295 also completes a maintaining circuit for the coil 2136* over contacts 205 2-08 and normally closed contacts 201 As the car approaches the third floor, the floor selector 22I opens the circuit feeding coil 286 but said circuit is maintained through contacts 205 296 and 201 At the same time selector 222 closes amomentary circuit for coil 288%, and relay 208 closes contacts Zilfi and thus energizes the circuit iorcoil 210 Relay 2-H] closes contacts 2H! and maintains itself and opens contacts 2MP, which deeenergizes coil 22% so that the retiring cam causes opening of the limit switch (225) at the third'floor. This de-energizes the coil 205 and the switch 2-235 disconnects the motor from the line. After a time sufliciently long for a passenger .to enter the car and register his call, if desired, the contact 265 reopens to ole-energize the coil 206 of switch 206. When the contact 205 opens, and if no more calls have been registered in the established direction of travel, the switch 206 is ole-energized. Shortly thereafter contacts 265 also open, thus ,de-energizing relay 2!!! and preventing its reclosure until the next stop is reached.

I'f relay 256 is still energized due to the con-- tinued closure of push buttons signalling for the car to travel in the previously established direction of travel, de-energization of relay 2H3 closes contacts 2 m thus re-establishing an energizing circuit for the retiring cam winding 226 which permits closure of the respective floor limit switch 22-5, thus energizing the main switch 205 to efiect operation of the motor as previously explained.

The operation upon closure of any other push button switch is apparent from the foregoing description, as it will also be apparent that having started in a given direction the elevator will stop at all floors in succession for which push buttons have been or are operated for effecting travel in that direction in the manner aforedescribed, and that'it will reverse to stop in response to push buttons for the other direction after it has completed its original direction of travel to the last station which has previously called. Operation of a push button in the car will stop the car at the respective floor upon its reaching said floor for the first time.

It will be apparent that the system aforedescribed afiords a control wherein calls which are registered remain registered until the elevator stops in response thereto, even if the electric power supply should temporarily fail or if the calls where initiated during such power failure.

What I claim .as new and desire to secure .by Letters Patent is:

I 1. A conveying system, comprising a car, car actuating means, a plurality of landing push button switches, at least one on each landing to be served by said car, a plurality ofcar push button switches in the car. at least one for each landing, said push button switches being operable to start said car actuating means to move said car to the corresponding landing and being provided with electromagneticaily releasable mechanical latching means to retain them in their opera-ted position, and means controlled bysaid car actuating means to cause the latter to respond in a predetermined order to the control by said push button switches, irrespective of the order of actuation of the latter, said last named means'including means to energize said latching means to cause return of the respective switches to their inoperative position in said order and thereby stop said car actuating means when said car reaches the respective landing.

2. An elevator system comprisin an elevator car, a reversible motor, a Winch connected to said motor and said car to move the latter between .a plurality of landings, a plurality of landing push button switches, at least one at each landing, a plurality of car push button switches in the car, at least one for each landing, said push button switches being operable to energize said motor for moving said car to the corresponding landing and being provided with electromagneticaily re.- leasable mechanical latching means to retain them in their operated position, means controlled by said winch to effect energization of said latching means to release said push button switches and interrupt energization of said motor when said car approaches the corresponding landing, and other means controlled by said winch and cooperating with said push button switches to selectively control the energization of said motor so as to operate it in the same direction to efiect itsstoppage at the respective landings in a predetermined order, independent of the order of actuation of said switches.

3. An elevator system comprising, an elevator car, a reversible motor, a winch connected to said motor and said car to move the latter between a plurality of landings, electromagnetic control means for said motor, a plurality of landing push button switches, at least one at each landing, a plurality of car push button switches in the car, at least one for each landing, said push button switches being operable to energize said electromagnetic control means to selectively start said motor in opposite directions and being pro, vided with electromagnetically releasable mechanical latching means to retain them in their operated position, a fioor selector coupled to said winch and arranged to energize said latching means to release said push button switches and thereby effect de-energization of said motor when said car approaches the corresponding landing, and commutating means coupled to said winch and connected in circuit with said push button switches to selectively control said electroma netic control means to cause said motor to move the car in the direction to effect its stoppage at the respective landings in a predetermined order, which is independentof the order of actuation of said switches.

4. An elevator system, comprising, an elevator car, a reversible motor, a winch connected to said motor and said car to move thela-tter between a plurality of landings, a plurality of landing push button switches, at least one at each landing, a plurality of car push button switches in-the car, at least one for each landing, said push button switches being operable to energize said motor for moving said car vto the corresponding landing and being provided with electromagnetic latching means to retain them in their operated position, means controlled by said winch to effect energization of said latching means to release said push button switches and interrupt energization of said motor when said car approaches the corresponding landing, other means controlled by said win h and cooperating with said push button switches to selectively control the energization of said motor so as to operate it in the direction to effect its stoppage at the respective landings in a predetermined order, independent of the order of actuation of said switches, and a push button switch in the car adapted to prevent response of any one of said releasing means at will.

5. An elevator system comprising, an elevator car, a hoisting machine for said car, including a reversible motor and adapted to move said car between a plurality of landings, an electromagnetic reversing switch for energizing said motor, a plurality of landing push button switches, at least one at each landing, a plurality of car push button switches in the car, at least one for each landing, said push button switches being operable to commutate an energizing circuit for said reversing switch to energize said motor for movement of said car to the corresponding landing and being provided with individual electromagnetic latching means to selectively retain them in their operated position and upon energization to release them therefrom, a commutator controlled by said car and adapted to energize said latching means and select said push button switches in a predetermined order independent of the order of their operation, a second commutator controlled by said car and connected in circuit with the energizing circuit of said reversing switch and arranged to de-energize the latter in said given order at the landings corresponding to the landing of the respective push button switches, and switch means to complete said energizing circuit of said reversing switch to start said car.

6. An elevator system comprising, an elevator car, a reversible motor, a winch connected to said motor and said car to move the latter between a plurality of landings, a plurality of landing push button switches, at least one at each landing, a plurality of car push button switches in the car, at least one for each landing, said push button switches being operable to permit energization of said motor for movement of said car to the corresponding landing and being provided with electromagnetic latching means to selectively retain them in their operated position and to release them therefrom, commutating means controlled by said winch and cooperating with said latching means to efiect release of said switches in a predetermined order independent of the order of operation of said switches, other commutating means controlled by said winch and in circuit with said push buttons and adapted to efiect energization of said motor and de-energization thereof at corresponding landings in said order, and a push button switch in said car adapted when operated to complete the circuit for eifecting energization of said motor to start the latter, and means to by-pass said last named switch after response of said motor energizing means.

'7. An elevator system comprising, a plurality of cars, car actuating means for each car, a plurality of floor push button switches, at least one on each floor to be served by said cars, a p1urality of car push button switches, at least one for each floor, in each car, said push button switches being provided with electromagnetically releasable mechanical latching means to retain 'them in their operated position, means in each car adapted to start said car in response to the operation of any of said floor push button switches and in response to the operation of any of said car push button switches in the respective car, which have been operated, means controlled by the actuating means of each car to cause the latter to respond in a predetermined order irrespective of the order of actuations of said push button switches to the control by the latter, and other means controlled by the actuating means of each car to energize said latching means of all of said floor push button switches and of the push button switches of said car to cause their return to their inoperative position in said predetermined order to thereby stop the actuating means of said car when said car approaches th respective floors.

8. An elevator system, comprising, a plurality of elevators, each comprising a car, car actuating means, a plurality of car buttons corresponding to the number of floors, said car buttons being operable to start said car actuating means to move said car to the corresponding floor and being provided with electromagnetically releasable mechanical latching means to retain them in their operated position, and means controlled by said car actuating means to cause the latter to respond in a predetermined order irrespective of the order of actuation of said car buttons to the control by the latter, said last named means including means to energize said latching means to cause return of the respective car buttons to their inoperative position in said predetermined order and thereby stop said car actuating means when said car approaches th respective floors, a plurality of floor call buttons, at least one on each floor to be served by said cars, and operable to start any of said plurality of car actuating means to move any one of said cars to the corresponding floor and being provided with electromagnetically releasable mechanical latching means to retain them in their operated position, and means controlled by each of said car actuating means to cause the latter to respond in said predetermined order to the control by said floor call buttons and to cause return of the respective car buttons to their inoperative position in said order and thereby stop the respective car actuating means when the corresponding car approaches the respective floors.

9. An elevator control system, comprising a car, car actuating means, a plurality of landing push button switches, at least one on each landing to be served by said car, a plurality of car push button switches in the car, at least one for each landing, said push button switches being operable to start said car actuating means to move said car to the corresponding landing and being provided with electromagnetically releasable mechanical latching means to retain them in their operated positions, and stopping means including means to energize said latching means to cause return of the respective switches to their inoperative positions and thereby stop said car actuating means when said car reaches the respective landing, said stopping means being controlled by said car actuating means and depending upon the sequence of operation of said push button switches and the position of the car for determining the initial direction of travel of said car, said stopping means being adapted during travel of the car in said direction to permit preselection by said push button switches to effect stoppage of said car prior to its arrival at its initially selected destination, and to effect travel of the car to a point or points beyond said destination, while insuring against reversal of the direction of travel of the car prior to arrival thereofat. the most remote preselected point in said direction of travel.

10. An elevator control system comprising, an elevator car, a reversible motor, a winch connected to said motor and said car to move the latter between a plurality of landings, a plurality of landing push button switches, at least one at each landing, a plurality of car push button switches in the car, at least one for each landing, said push button switches being operable to energize said motor for moving said car to the corresponding landing and being provided with electromag'netically releasable mechanical latching means to retain them in their operated positions, and stopping means including means to energize said latching means to cause return of the respective switches to their inoperative positions and thereby interrupt energizationof said motor when said car approaches the corresponding landing, said stopping means being controlled by said Winch and depending upon the sequence of energization of said push button. switches and the position of said car for determining the initial direction of travel of said car, said stopping means being adapted during travel of the car in said direction to permit preselection by said push button switches to effect stoppage of the car prior to its arrival at its initially selected destination, and to effect travel of the car to a point or'points beyond said destination, while insuring against reversal of the direction of travel of the car prior to arrival thereof at the most remote preselected point in said direction of travel.

EIVIND U. LASSEN. 

